U.S.Capitol Police surround a car with their guns drawn at the corner of Pennsylvania Avenue and 1st Street, northwest in this image from Alhurra TV video in Washington on Thursday.

The Secret Service and Capitol Police were unable to communicate with each other by radio during critical moments after a woman tried to ram a car through a barrier at the White House, then was chased past the Capitol before being shot to death.

Sources close to the investigation said Friday that the inability will be a focus during police reviews of Thursday’s incident.

Terrance Gainer, sergeant at arms of the U.S. Senate, confirmed that the radio systems of the Secret Service and the Capitol Police operate on different frequencies and were unable to directly communicate as Miriam Carey raced down Pennsylvania Avenue toward the Capitol.

“The Capitol Police radios don’t talk to the Secret Service radios and neither of them talk to the MPD” (Washington Police Department), Gainer told NBC News.

Spokesmen for the Secret Service and Capitol Police did not respond to requests for comment.

The inability of law enforcement and first responder radios to communicate has been an issue for years and was sharply criticized by the 9/11 Commission. In this week’s incident, NBC station WRC of Washington reported Friday that the inability of Secret Service officers to alert Capitol Police of Carey’s approach deprived the police officers of a crucial 30 to 45 seconds they could have used to put up perimeter barriers.

Diagnosed with depression and psychosis, Miriam Carey had recently stopped taking her medications, according to investigators. They say travel records show she drove directly from Connecticut to Washington, D.C., on Thursday, when the chaos began. NBC's Pete Williams

Carey initially drove into the driveway leading to the White House at about 2:12 p.m. Thursday, hit some temporary fencing, then backed up, striking a Secret Service officer, who suffered minor injuries.

Officers told the driver to stop and placed a temporary barrier placed behind her car, and the driver backed into this fence and sped away, said law enforcement officials, who provided new details about the incident to NBC News on condition of anonymity.

The officials said Secret Service officers pursued her at high speed southeast on Pennsylvania Avenue.

The car was cornered near Garfield Circle and the Capitol Reflecting Pool a few minutes later. Video shot by the U.S.-funded Alhurra news network shows six officers with guns drawn approached the stopped car and attempted to order the driver from the vehicle. Carey whipped the car around, scattering the officers.

The chase ended minutes later at the northeast corner of the Capitol grounds, near the U.S. Supreme Court building, when a barrier stopped the Infiniti near Second Street Northeast. The officials said she became stuck on a median by a Capitol Police guard post, where she was shot dead.